Such a device is described by DE 10055182 A1. This device comprises a quartz tube within which a process chamber is located. The process chamber wall comprises a number of graphite elements, that is a top, two walls and a bottom. The individual graphite wall elements engage against one another in touching contact. The known device is surrounded by an RF coil, which generates an RF field inside the reactor housing. Said field produces eddy currents in the process chamber walls. As a result of the contact resistances in the regions where the individual wall elements engage against one another, instances of local heating or even spark discharges occur.